1. Field of the Invention
The present invention relates to an explosive powder-charge operated setting tool including a guide cylinder having a bore, a drive piston displaceably supported in the bore of the guide cylinder and having a stop surface facing in a direction opposite to setting direction, a carrier having, in its end region facing in a direction opposite to the setting direction, a catridge-receiving chamber and a first active surface facing in the setting direction and from which a cylindrical projection extends, with an end surface of the cylindrical projection facing in the setting direction forming a second active surface, and with the stop surface of the drive piston cooperating with the active surface of the support, with the drive piston having a cylindrical recess extending from the stop surface in the setting direction and in which the cylindrical projection of the carrier is received.
2. Description of the Prior Art
For driving fastening elements in hard constructional components, such as concrete, rock, or steel, setting tool, which are driven by propellant means--containing catridges, are used. One of such setting tool is disclosed in French patent No. 1,355,370. The setting tool disclosed in the French patent has a drive piston displaceable in a guide cylinder, and a carrier having a catridge-receiving chamber.
The drive piston is supported in the running bore of the guide cylinder with a possibility of displacement relative to the guide cylinder. The carrier is provided in an end of the guide cylinder facing in a direction opposite to the setting direction and is connected with the guide cylinder. The carrier has a first active surface which is formed by an end surface of the carrier facing in the setting direction and a catridge-receiving chamber formed in an end of the carrier facing in a direction opposite to the setting direction. A central cylindrical projection extends from the first active surface in the setting direction. The cylindrical projection is provided with a second active surface likewise facing in the setting direction. The carrier further includes a connection bore which connects the catridge-receiving chamber with the bore of the guide cylinder.
The drive piston has, in its end facing in the direction opposite to the setting direction, a recess opening in the direction opposite to the setting direction. The inner diameter of this recess substantially corresponds to the outer diameter of the cylindrical projection of the carrier. Because of this, upon ignition of a catridge, a high initial acceleration is sharply reduced to a much smaller acceleration as soon as the projection leaves the recess in the drive piston in which it is received. This sharp transition from a high acceleration to a low acceleration results in a sharp pressure drop in the combustion chamber which, in turn, results in incomplete combustion of the propellant means. The incomplete combustion of the propellant means leads to an excessive soiling of the setting tool.
Accordingly, an object of the present invention is to provide an explosive powder charge-operated setting tool in which complete combustion of the propellant means takes place after the initial high acceleration following the ignition of the catridge.
Another object of the present invention is to provide an explosive powder charge-operated setting tool in which a uniform transition from the initial high acceleration to the smaller acceleration takes place, so that no sharp pressure drop occurs in the combustion chamber.